[英]Capture the error output of a foreground command using plumbum
I'm using the plumbum python library (http://plumbum.readthedocs.org/) as a replacement for shell scripts. 我使用plumbum python库(http://plumbum.readthedocs.org/)作为shell脚本的替代品。
There's a command I want to run that, when it fails it outputs the paths to a file I'm interested in: 有一个我想要运行的命令,当它失败时它会输出我感兴趣的文件的路径:
$ slow_cmd
Working.... 0%
Working.... 5%
Working... 15%
FAIL. Check log/output.log for details
I want to run the program on the foreground to check the progress: 我想在前台运行程序来检查进度:
from plumbum.cmd import slow_cmd
try:
f = slow_cmd & FG
except Exception, e:
print "Something went wrong."
# Need the error output from f to get the log file :(
When the slow_cmd
fails, it throws the exception (which I can catch). 当
slow_cmd
失败时,它会抛出异常(我可以捕获)。 But I cannot obtain the error output from the exception or from the f
future object. 但我无法从异常或
f
future对象获取错误输出。
If I don't run the slow_cmd
on the FG, the exception contains all of the output and I can read the file from there. 如果我没有在FG上运行
slow_cmd
,则异常包含所有输出,我可以从那里读取文件。
the problem is, FG
redirects the output straight to your program's stdout. 问题是,
FG
将输出直接重定向到程序的标准输出。 see https://github.com/tomerfiliba/plumbum/blob/master/plumbum/commands.py#L611 请参阅https://github.com/tomerfiliba/plumbum/blob/master/plumbum/commands.py#L611
when output is redirected this way, it doesn't go through plumbum's machinery so you won't get it in the exception object. 当输出以这种方式重定向时,它不会通过plumbum的机器,所以你不会在异常对象中得到它。 if you're willing to block until
slow_cmd
finishes, a better solution would be to read from stdout yourself. 如果你愿意阻止,直到
slow_cmd
完成,一个更好的解决方案是自己读取stdout。 here's a sketch: 这是草图:
lines = []
p = slow_cmd.popen()
while p.poll() is None:
line = p.stdout.readline()
lines.append(line)
print line
if p.returncode != 0:
print "see log file..."
a more elegant solution would be to write your own ExecutionModifier (like FG
) that duplicates the output streams. 更优雅的解决方案是编写自己的ExecutionModifier(如
FG
),复制输出流。 let's call it TEE
(after http://en.wikipedia.org/wiki/Tee_(command) )... i haven't tested it, but it should do the trick (minus select
ing on stdout/err): 让我们称之为
TEE
(在http://en.wikipedia.org/wiki/Tee_(command)之后 )...我还没有测试过它,但它应该做的伎俩(减去select
stdout / err):
class TEE(ExecutionModifier):
def __init__(self, retcode = 0, dupstream = sys.stdout):
ExecutionModifier.__init__(self, retcode)
self.dupstream = dupstream
def __rand__(self, cmd):
p = cmd.popen()
stdout = []
stderr = []
while p.poll():
# note: you should probably select() on the two pipes, or make the pipes nonblocking,
# otherwise readline would block
so = p.stdout.readline()
se = p.stderr.readline()
if so:
stdout.append(so)
dupstream.write(so)
if se:
stderr.append(se)
dupstream.write(se)
stdout = "".join(stdout)
stderr = "".join(stderr)
if p.returncode != self.retcode:
raise ProcessExecutionError(p.argv, p.returncode, stdout, stderr)
return stdout, stderr
try:
stdout, stderr = slow_cmd & TEE()
except ProcessExecutionError as e:
pass # find the log file, etc.
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